Guide templates for surgical implants and related methods

ABSTRACT

A guide template for use in resurfacing a portion of a bone includes a body adapted for positioning over a natural or resected articulation surface of the bone. The body has a top surface and an opposing bottom surface that each extend between a proximal end and an opposing distal end. The body at least partially bounds an opening extending between the top surface and the bottom surface. At least a portion of the top surface or the bottom surface has a convex curvature or a concave curvature that extends between the proximal end and the opposing distal end. At least three spaced apart supports project below the bottom surface of the body such that the body can be supported by the supports. Fasteners are provided for securing the body to the bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/901,941, filed Jul. 28, 2004, which claims priority to U.S.Provisional Application Ser. No. 60/586,706, filed Jul. 9, 2004, whichapplications are incorporated herein by specific reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to instruments and methods for preparingan orthopedic joint articulation surface to receive a bearing implant.

2. The Relevant Technology

The human body has a variety of movable orthopedic joints such as theknee joint, hip joint, shoulder joint, and the like. These joints areformed by the intersection of two bones. The intersecting end of eachbone has smooth articular surface that is comprised of cartilage. As aresult of injury, wear, arthritis, disease or other causes, it isoccasionally necessary to replace all or part of an orthopedic jointwith an artificial implant. This procedure is referred to as a jointreplacement or arthroplasty. For example, a total knee arthroplastycomprises cutting off or resecting the articular surfaces at both thedistal end of the femur and the proximal end of the tibia. Complementaryartificial implants are then mounted on the distal end of the femur andthe proximal end of the tibia. Where only a portion of a joint isdamaged, a partial joint arthroplasty can be performed. In thisprocedure, one or more artificial implants replace only a portion of ajoint.

Although joint replacement is now a common procedure that has met withpopular success, conventional implants and related mounting techniqueshave significant shortcomings. One significant drawback of many jointreplacements is the extended and painful patient recovery. For example,a traditional knee replacement requires an open procedure wherein arelatively large incision is made which severs a portion of the musclebounding the femur. The large incision is made so as to fully expose therespective ends of the femur and tibia.

This exposure is necessary when using conventional techniques to resectthe femur and tibia and to mount the implants. For example, someconventional tibial implants are screwed directly into the resected endface of the tibia. Mounting such screws requires exposure of theresected end face. In yet other embodiments, the implants are formedwith posts projecting therefrom. The posts are received within socketsformed on the resected end face of the tibia and femur. Again, formingof the sockets and inserting the posts into the sockets requiressubstantially full exposure of the resected end face of the tibia andfemur.

In general, the more invasive the surgery, the more painful, difficult,and time consuming the patient recovery. This is largely due to thesignificant amount of scar tissue produced by the incision and resectionof various soft tissues. Furthermore, such open and invasive surgerieshave a greater risk of infection.

Another problem with conventional joint implants and related techniquesfor mounting is that it can be difficult to fit, adjust, and/or exchangedifferent implants during the fitting stage. That is, implants come in avariety of different sizes, shapes, and configurations. During the jointreplacement procedure, the surgeon may often test a variety of differentsized implants to determine the best fit and alignment. As conventionalimplants are screwed into or pounded onto the bone during placement, thefitting, adjustment, and/or replacement of different conventionalimplants can be difficult and potentially damaging to the bone.Likewise, it can often be difficult to replace worn or damaged implants.

Accordingly, what is needed are implants and related methods and systemsfor preparing an articular surface of a joint and mounting an implantthereat which minimizes the length of incision, the amount of boneresection, and/or the impact on soft tissue. What is also needed areimplants and related methods and systems which enable easier fitting,alignment, testing, and/or replacement of implants.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 is a perspective view of the proximal end of a tibia;

FIG. 2 is a perspective view of the tibia shown in FIG. 1 having atunnel formed thereon;

FIG. 3 is a perspective view of the tibia shown in FIG. 4 having arecessed pocket formed thereon;

FIG. 4 is a perspective view of the tibia shown in FIG. 1 on which aflat resected surface has first been formed prior to forming the pocketthereon;

FIG. 5A is a top perspective view of a condylar implant;

FIG. 5B is a bottom perspective view of the condylar implant shown inFIG. 5A;

FIG. 5C is an exploded perspective view of the condylar implant shown inFIG. 5B;

FIG. 6A is an exploded perspective view of an alternative embodiment ofa condylar implant having two pockets;

FIG. 6B is a bottom perspective view of the implant shown in FIG. 6Awith a line for connecting thereto;

FIG. 7 is a bottom perspective view of another alternative embodiment ofa condylar implant having three pockets;

FIG. 8 is a perspective view of a unitary condylar implant having spikesformed thereon;

FIG. 9 is a cross sectional side view showing a wire attached to animplant by crimping;

FIG. 10 is a cross sectional side view showing a wire attached to animplant by looping around a hook;

FIG. 11 is a cross sectional side view showing a wire attached to animplant by passing through a constricted opening in the implant;

FIG. 12 is a cross sectional side view showing a wire attached to animplant by a set screw;

FIG. 13 is a cross sectional side view showing a wire attached to animplant by a barbed retainer;

FIG. 14 is a bottom perspective view of an alternative embodiment of animplant having a line slidably connected thereto;

FIG. 15 is an exploded view of an anchor assembly for securing acondylar implant to a tibia;

FIG. 16 is an enlarged perspective view of the anchor assembly shown inFIG. 15 including a bone anchor and a lock;

FIG. 17 is a cross sectional side view of the bone anchor shown in FIG.16;

FIG. 18 is an elevated front view of the lock shown in FIG. 16;

FIG. 19 is a cross sectional side view of the assembled anchor assemblyshown in FIG. 16 having a line extending therethrough;

FIG. 20 is a perspective view of an implant mounted on a tibia with theanchor assembly of FIG. 19 being mounted to the tibia;

FIG. 21 is an elevated front view of a tensioner;

FIG. 22 is an elevated side view of the tensioner shown in FIG. 21;

FIG. 23 is a perspective view of the tensioner shown in FIGS. 21 and 22coupled with the mounted anchor assembly shown in FIG. 20;

FIGS. 24A and 24B are perspective views of alternative embodiments ofbone anchors;

FIG. 25 is a perspective view of a system used to secure the implantshown in FIG. 14 to the tibia;

FIG. 26 is a perspective view of a guide template mounted on a medialcondyle of a femur and a milling head disposed within an opening of theguide template;

FIG. 27 is a perspective view of a rasp that is selectively used withthe guide template shown in FIG. 26;

FIG. 28 is a perspective view of the rasp shown in FIG. 46 being usedwith the guide template of FIG. 26;

FIG. 29 is a top perspective view of a femoral condylar implant;

FIG. 30 is a bottom perspective view of the femoral condylar implantshown in FIG. 29 having a line connected thereto;

FIG. 31 is a perspective view of the system shown in FIG. 23 being usedto secure the femoral condylar implant of FIG. 29 to the femur;

FIG. 32 is a perspective view of guide template mounted on the distalend of the femur;

FIG. 33 is a top perspective view of the guide template shown in FIG.32;

FIG. 34 is a bottom perspective view of the guide template shown in FIG.32;

FIG. 35 is a perspective view of the rasp mounted on the guide templateshow in FIG. 32;

FIG. 36 is an elevated side view of the rasp shown in FIG. 35;

FIG. 37 bottom plan view of the rasp shown in FIG. 35;

FIG. 38 is an elevated back view of the rasp shown in FIG. 35;

FIG. 39 is a bottom plan view of the rasp and guide template shown inFIG. 35;

FIG. 40 is a perspective view of the femur shown in FIG. 35 having arecessed pocket formed by the rasp;

FIG. 41A is a back perspective view of the cutting mount for the raspshown in FIG. 36;

FIG. 41B is a back perspective view of an alternative embodiment of thecutting mount shown in FIG. 41A;

FIG. 42 is an alternative embodiment of a rasp;

FIG. 43 is a top perspective view of a trochlear groove implant withFIG. 43A being a cross section thereof;

FIG. 44 is a back perspective view of the trochlear groove implant shownin FIG. 43 in a disassembled state;

FIG. 45 is a back perspective view of the trochlear groove implant shownin FIG. 43 with a line connected thereto;

FIG. 46 is a perspective view of the femur shown in FIG. 40 with theimplant shown in FIG. 43 mounted in the pocket thereof;

FIG. 47 is a top perspective view of an alternative embodiment of theguide template shown in FIG. 32;

FIG. 48 is a bottom perspective view of the guide template shown in FIG.47;

FIG. 49 is a disassembled view of the guide template shown in FIG. 47;

FIG. 50 is a perspective view of the base of the guide template shown inFIG. 46 with guide sleeves and screws;

FIG. 51 is a top plan view of the base shown in FIG. 50 with a raspmounted thereon;

FIG. 52 is a bottom plan view of the base and rasp shown in FIG. 51;

FIG. 53 is a top perspective view of another alternative embodiment of aguide template;

FIG. 54 is a top perspective view of the guide template shown in FIG. 53in a disassembled state;

FIG. 55 is a bottom perspective view of the guide template shown inFigure 53 in a disassembled state;

FIG. 56 is a bottom perspective view of the guide template shown in FIG.53;

FIG. 57 is a perspective view of the guide template shown in FIG. 53with an alternative embodiment of a rasp; and

FIG. 58 is a perspective view of the rasp shown in FIG. 57.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to methods and apparatus for preparing anarticulation surface of an orthopedic joint to receive an implant,implants for mounting at an articulation surface of an orthopedic joint,anchoring systems for securing an implant at an articulation surface ofan orthopedic joint, and related methods and instruments. As used in thespecification and appended claims, the terms “articulation surface” and“natural articulation surface” are broadly intended to include allnatural articular surfaces of a bone forming a portion of an orthopedicjoint and all articulation wear surfaces of a bone forming a portion ofan orthopedic joint which are produced as a result of ware, trauma,disease, or other causes which remove all or a portion of the naturalarticular surface.

The implants, anchoring systems, instruments, and methods of the presentinvention can be used in combination to mount an inventive implant orcan be used separately or in combinations with other conventionalimplants, anchoring systems, instruments and/or methods. It isappreciated that the implants, anchoring systems, instruments, andmethods of the present invention can be used for mounting an implant onvirtually any articulation surface of any orthopedic joint in a human orother mammal. By way of example and not by limitation, the implants,anchoring systems, instruments, and methods of the present invention canbe used in association with resurfacing an articulation surface of aknee joint, ankle joint, hip joint, shoulder joint, elbow joint, wristjoint, interphalangeal joint, or other joints. As such, the implants canbe mounted on the proximal end and distal end of the femur, tibia,humerus, radius, and ulna, and on the articular surfaces of the scapula,pelvis, bones within the foot and hand, and other bone articularsurfaces. Likewise, the implants, anchoring systems, instruments, andmethods of the present invention can be used in facilitating a partialjoint arthroplasty or a total joint arthroplasty.

In one embodiment, the implants, anchoring systems, instruments, and/ormethods of the present invention are designed so that an articulationsurface of a joint can be prepared and an implant mounted thereon usingprocedures that are minimally invasive. As a result, recovery time issignificantly improved while the damage to soft tissue if decreased andthe risk of infection minimized. Also in one embodiment of the presentinvention, the implants, anchoring systems, instruments, and/or methodsare designed so that the implant can be selectively adjusted, tightened,and/or loosened after the implant is positioned on the articulationsurface. This ability allows for greater ease in adjustment and fittingof an implant at the time of initial placement and for greater easy inreplacement of an implant.

Set forth below are several embodiments of the present invention used inassociation with preparing an articulation surface at a proximal end ofa tibia and mounting a condylar implant at the proximal end of thetibia. It is again noted that these embodiments are only given by way ofexample and that one skilled in the art based on the teaching providedherein would be able to use corresponding implants, methods, andinstruments to prepare and/or mount an implant on other jointarticulation surfaces.

Depicted in FIG. 1 is a proximal end 10 of a tibia 12. Proximal end 10has a lateral side 14 and a medial side 16 which each extend between ananterior side 18 and a posterior side 19. Proximal end 10 furthercomprises a lateral condyle 20 and a medial condyle 21. Lateral condyle20 terminates proximally at a lateral facet 22 of a superior articularsurface of tibia 12 while medial condyle 21 terminates proximally atmedial facet 24 of a superior articular surface of tibia 12.

Although tibia 12 shown in FIG. 1 is from a left leg, it is appreciatedthat the tibia of the right leg has a complimentary configuration andthat the methods and apparatus of this specific example are equallyapplicable thereto. Furthermore, the methods and apparatus of thisexample are primarily illustrated in association with medial condyle 21of tibia 12. It is also appreciated that the methods and apparatus canbe used in association with lateral condyle 20.

In one embodiment, to facilitate mounting of a condylar implant onmedial condyle 21, conventional arthroscopic procedures are used toresect the posterior portion of the medial meniscus. Once the posteriorportion of the medial meniscus is removed, a vertical or horizontalincision, generally in a range between about 2 cm to about 6 cm, isformed over the anterior side of the medial meniscus. Followingretraction of the surrounding tissue, the anterior side of the medialmeniscus is resected. A coarse rasp is then inserted between the medialcondyle of the femur and medial condyle 21 of tibia 12. The rasp is usedto remove approximately 1-2 mm of articular cartilage on medial facet 24of tibia 12. Removal of the meniscus and the articular cartilageprovides increased access to medial facet 24 of tibia 12.

Depicted in FIG. 2, a tunnel 400 is formed through a portion of tibia12. Tunnel 400 can be used for preparing tibia 12 for a condylar implantand/or securing a condylar implant to tibia 12. Tunnel 400 has aninterior surface 401 that extends from a first end 402 to an opposingend second end 404. First end 402 is formed on medial side 16 ofproximal end 10 of tibia 12. Second end 404 is formed on medial facet 24of tibia 12. Expressed in other terms, second end 404 of tunnel 400 isformed on a section of an articulation surface, i.e., medial facet 24,while first end 402 is at a location on tibia 12 that is spaced apartfrom the articulation surface. Although tunnel 400 can be any desiredsize, in one embodiment tunnel 400 has a diameter in a range betweenabout 5 mm to about 10 mm. In alternative embodiments, it is appreciatedthat first end 402 of tunnel 400 can be positioned at any desiredlocation at proximal end 10 of tibia 12. For example, first end 402 canbe positioned at lateral side 14 or anterior side 18.

Tunnel 400 is typically formed using a drill in combination with one ofa variety of different types of guide assemblies. Alternative methodsand techniques for forming tunnel 400 are disclosed in U.S. patentapplication Ser. No. 10/901,941, filed Jul. 28, 2004 which isincorporated herein by specific reference (hereinafter “the '941application”).

Using the above-referenced methods and instruments, tunnel 400 can beformed by procedures that are minimally invasive to the patient. Oncetunnel 400 is formed, tunnel 400 can then be used to assist in theresection of medial fact 24 and/or the mounting of a condylar implant onthe resected medial facet 24. Furthermore, by using tunnel 400 theresection of medial facet 24 and the mounting of the condylar implantcan also be performed using procedures that are minimally invasive.

Depicted in FIG. 3, a recessed pocket 194 is formed on medial facet 24.Pocket 194 is formed so as to intersect with Second end 404 of tunnel400 and is contoured to receive a condylar implant. It is appreciatedthat pocket 194 can be formed using a variety of different methods andinstruments including templates, guides, mills, rasps and combinationsthereof. In one embodiment, tunnel 400 can be used in the formation ofpocket 194. In alternative embodiments, pocket 194 can be formedindependent of tunnel 400. For example, depicted in FIG. 4 tibia 12 hasbeen prepared to receive a condylar implant by first resecting medialcondyle 21 so as to form a flat resected surface 234. Next, recessedpocket 194 is formed on resected surface 234 using a rasp or otherinstrument. Finally, tunnel 400 is formed extending from lateral side 14of tibia 12 to pocket 194. In this latter approach, it is appreciatedthat pocket 194 can first be formed followed by the formation of tunnel400. Examples of different methods and instructions that can be used inthe formation of resected surface 234 and pocket 194 are disclosed inthe '941 application.

As will be discussed below in greater detail, a bone anchor is securedwithin first end 402 of tunnel 400. The bone anchor requires a largeropening than what is necessarily needed for a line or fastener to passthrough tunnel 400. Accordingly, where tunnel 400 is minimized to limitbone removal, first end 402 of tunnel 400 can be counter bored with alarger drill so as to enable proper placement of the bone anchor. In oneembodiment, tunnel 400 can be counter sunk so as to have a diameter in arange between about 4 mm to 8 mm. Again, other dimensions can also beused.

Depicted in FIGS. 5A-C is one embodiment of a condylar implant 300incorporating features of the present invention. The term “condylarimplant” is broadly intended to include implants that can replace all ora portion of a condyle. The condylar implant can also replace all or aportion of the articulation surface of the condyle. Accordingly, whilethe depicted embodiments show one conventional size and configurationfor a condylar implant, in alternative embodiments the condylar implantcan be larger to replace more of the tibia or can be smaller to replaceonly a section of a condyle of a tibia. In such alternatives, thecondylar implant can have a variety of different configurations.

In general, condylar implant 300 has a top articular surface 306 and anopposing bone apposition surface 303. In one embodiment, top articularsurface 306 has a generally concave contour that continuously curvesfront to back and side to side so as to mate with a correspondingfemoral condyle. Alternatively, articular surface 306 can besubstantially flat. Bone apposition surface 303 has a generally convexcontour that continuously curves front to back and side to side and thatis configured to mate with pocket 194 (FIGS. 3 and 4). In oneembodiment, articular surface 306 is substantially complementary to boneapposition surface 303. As a result of contouring bone appositionsurface 303, implant 300 can be formed having a low profileconfiguration with a generally uniform thickness along the length andwidth thereof. This uniform thickness provides uniform strength forimplant 300. Furthermore, by contouring implant 300 to fit within pocket194, the stability of mounted implant 300 is increased so as to preventunwanted movement of implant relative to tibia 12.

In alternative embodiments, bone apposition surface 303 can besubstantially flat. As a result, implant 300 can be mounted directly onflat resected surface 234. In this embodiment, however, contouring ofarticular surface 306 would result in the opposing ends of implant 300being thicker than the middle. Again, however, depending on the size ofthe patient and the portion of the bone being replaced, implant 300 canhave an array of different sizes and configurations.

As depicted in FIG. 5C, implant 300 comprises a body 301 and an inlay320. Body 301 has top articular surface 306 and an opposing bottomsurface 308. A pocket 316 is recess on bottom surface 308. Pocket 316 isbounded by a floor 317 and a sidewall 318 upstanding around theperimeter thereof. A stem 304 projects from floor 317 and is completelyencircled by pocket 316. Body 301 is typically comprised of a metal suchas chromium, cobalt, titanium, or the like and alloys thereof but canalso be made of ceramics, plastics, or other materials. Body 301 canalso be comprised of layers or sections of different materials. In oneembodiment, body 301 has a maximum thickness typically in a rangebetween about 2 mm to about 10 mm. Other dimensions can also be useddepending on the amount that the tibial condyle is resected or wornaway.

Inlay 320 is secured within pocket 316 of body 301 so as to encirclestem 304. Inlay 320 is comprised of a porous bone ingrowth material suchas porous tantalum. Other conventional porous bone ingrowth materialscan also be used. Inlay 320 is secured within pocket 316 usingconventional techniques such as press fit, welding, adhesive, sintering,and the like. Inlay 320 can also be mechanically connected to body 301such as by screws, fasteners, rivets, or the like. In alternativeembodiments, pocket 316 can be eliminated and inlay 320 can be securedto the bottom surface of body 301 using various techniques. Inlay 320has an exposed bottom surface 322 that, as discussed above, can bearched, substantially flat, or can have any other desired configuration.In this embodiment, bottom surface 322 of inlay 320 comprises.substantially all of bone apposition surface 303 of base plate 301.

In contrast to having a single pocket 316 in which a single inlay 320 ispositioned, it is appreciated that body 301 can be formed having aplurality of pockets each adapted to receive a separate inlay. Forexample, depicted in FIGS. 6A and B is an alternative embodiment of animplant 410 comprising a body 412 having a bottom surface 414. Bottomsurface 414 is formed with two pockets 416A and B which are partiallybounded by a perimeter sidewall 418 and are separated by a centralbridge 420. Each pocket 416A and B is adapted to receive a correspondinginlay 422A and B. In this embodiment, the bone apposition surfaceincludes not only the bottom surface of inlays 422A and B but also thebottom surface of bridge 420 and perimeter sidewall 418.

Similarly, depicted in FIG. 7 is an alternative embodiment of a body 424for an implant. Body has a bottom surface 424 with three separatepockets 426A, B, and C. Each of the pockets 426 is adapted to receive aseparate inlay. The bridges formed between the separate pockets provideincreased structural support for the implant and, as will be discussedbelow in greater detail, provide a structure on which a flexible linecan be attached.

In still other embodiments, it is appreciated that the inlay of porousbone ingrowth material can be eliminated. In this embodiment, thecondylar implant can comprise a single integral member. For example,depicted in FIG. 8 is an alternative embodiment of a condylar implant428. Implant 428 is formed as a single integral body 430 having toparticular surface 306 and an opposing bottom surface 430 which alsofunctions as the bone apposition surface. To facilitate secureattachment of implant 428 to tibia 12, a plurality of spikes 434 areformed on bottom surface 430. It is appreciated that in all of theembodiments herein that spikes, fins, or other forms of projections canalso be formed projecting from bottom surface of the implant. Suchprojections can be separated from or encircled by the porous boneingrowth inlay. The projections can also be formed on the porous boneingrowth inlay. Such projections can penetrate into the tibia or bereceived within slots formed on the tibia to help prevent unwantedmovement of the implant.

In one embodiment, a flexible line is used to secure the implants totibia 12. As used in the specification and append claims, the term“line” is broadly intended to include wire, cable, cord, suture, bradedline, combinations thereof or any other type of flexible filament. Theline can be made of metal, alloys, synthetics, composites, or any otherdesired material. In one embodiment of the present invention the linecomprises braded filaments of a cobalt chrome alloy having a diameter ina range between about 0.25 mm to about 5 mm with about 0.5 mm to about 3mm being more common and about 0.5 mm to about 2 mm being most common.Other dimensions can also be used. The line can be of any desiredlength.

In one embodiment, the line can also be defined in that for anunsupported length of line of 4 cm, the line has substantially nocompressive strength. In yet other embodiments, for an unsupportedlength of line of 4 cm, the line fails under buckling when an axialcompressive load of 0.25 Newtons (N), 1 N, 2 N, 5 N, 20 N, or 50 N isapplied. That is, different lines can be used that fail under differentloads. Stiffer lines can also be used.

It is also appreciated that the line can be static or resilientlystretchable. In one embodiment where the line is resilientlystretchable, the line can be comprised of a material have shape memoryof pseudo elastic properties. One example of such a material is a nickeltitanium alloy sold under the name Nitinol. In yet other embodiment, itis appreciated that sections of the line could be replaced with a springmember such as a coiled spring or rubber or bungee type member.

Returning to FIGS. 5B and C, an elongated line 438 is provided having afirst end 439 and an opposing second end 440. First end 439 terminatesat a tip 441 that is sealed so as to have and maintain a smoothuniformed diameter. Second end 440 terminates at an enlarged roundedhead 442. In alternative embodiments, second end 440 can have the sameconfiguration as first end 439 or can have an enlarged head of anydesired configuration.

In one embodiment of the present invention, means are provided forconnecting flexible line 438 to implant 300. By way of example and notby limitation, stem 304 is provided with a threaded socket 312. Slidablydisposed on line 438 is a tubular retainer 444. Retainer 444 comprises abody 445 having one or more helical threads 446 mounted on the exteriorsurface thereof. Threads 446 are configured to engage with threadedsocket 312. A channel 448 longitudinally extends through body 445.Channel 448 constricts toward the distal end of body 445 so that thechannel 448 thereat is larger than the diameter of line 438 but smallerthan the diameter of head 442. The proximal end of channel 448 isenlarged and has a polygonal transverse cross section. As a result,first end 439 of line 438 can be passed through channel 448 of body 445distal to proximal. Line 438 can then be pulled through retainer 444until head 442 is stopped by the constricted section of channel 448. Thefirst end of line 438 can then be advanced through a central channel ina tubular driver (not shown) having a free end adapted to fit withinchannel 448 of retainer 444 at the proximal end thereof. The driver canthus be used to screw retainer 444 into threaded socket 312, therebysecuring line 438 to implant 300.

Depicted in FIG. 6B is another embodiment of the means for connecting aline to an implant. In this embodiment a passage 464 extends throughbridge 420. Passage 464 has an entrance 465 formed on a side wall ofbridge 420 and an exit 466 formed on a bottom surface of bridge 420.Again, passage 464 constricts as it extends from entrance 465 to exit466. Line 438 is shown having an enlarged substantially cylindrical head442 formed on second end 440. Head 442 is larger than the constrictedportion of passage 464. Head 442 can be crimped, welded, or otherwiseformed on line 438. Head 442 can also be integrally formed with line438. During assembly, first end 439 of line 438 is passed throughpassage 464 from entrance 465 to exit 466. Line 438 is advanced throughpassage 464 until head 442 is captured and securely retained withinconstricted passage 464. Inlays 422A and B can then be positioned withinpockets 416A and B. In yet other embodiments, rather than constrictingpassage 464, it is appreciated that head 442 can be wedge shaped so thathead 442 is captured within passage 464.

Depicted in FIGS. 9-14 are a variety of still other embodiments of themeans for connecting a line to an implant. Specifically, depicted inFIG. 9 is a stem 450 mounted to implant 300 which can be selectivelycrimped so as to catch head 442 within stem 450. In one embodiment thiscan be accomplished by forming slots along stem 450. Depicted in FIG.10, a hook 452 is formed projecting from the bottom surface of body 301of implant 300. In contrast to having head 442, a loop 454 is formed atthe second end of line 438. Loop 454 is looped around hook 452. Inlay320 is then mounted on the bottom surface of body 301 so as to preventloop 454 from accidentally sliding off of hook 452.

Depicted in FIG. 11, a channel 456 can be formed extending throughimplant 300 from top surface 306 to bottom surface 308. Channel 456 isenlarged at top surface 306 so as to receive head 442 of line 438 butconstricts toward bottom surface 308 so as to capture head 442 withinchannel 456. The opening to channel 456 on top surface 306 can berounded to prevent unwanted wear on the femoral condyle. In otherembodiments, a plug can be inserted within channel 456 so as to occludethe opening to channel 456. In still another alternative, instead offorming the opening to channel 456 top surface 306, a constricted slotcan be formed that inwardly extends from the side of implant 300.

Depicted in FIG. 12, a set screw 458 is screwed into the side of atubular stem 459 to capture head 456 therein. Finally, depicted in FIG.13, rather than having a threaded retainer 444 as discussed above, atubular retainer 460 can be provided with outwardly projecting barbs461. Retainer 460 can simply be pushed into a socket 462 having threadsor barbs thereon so that retainer 460 is captured therein. It is alsonoted that in FIG. 13 line 438 is shown comprising a resilientlystretchable spring 468. It is appreciated the spring 468 can be directlyconnected to the implant or disposed along line 438. Spring 468 can alsocome a variety of different shapes and sizes and be made from differentmaterials. As will be discussed below in greater detail, spring 468helps maintain the desired tension force on line 438 so that the implantis securely held in position.

In the embodiment depicted in FIG. 14, an implant 470 has a body 471with a bottom surface 472. A pair of spaced apart projections 474A and Bproject from bottom surface 472. A passage 475 extends through eachprojection 474A and B. Line 438 is passed through each passage 475 sothat line 438 is slidably connected to implant 470 with both ends 439and 440 of line 438 being freely disposed. As will be discussed below ingreater detail, in this embodiment both ends 439 and 440 of line 438 areseparately connected to the bone. Since line 438 is slidably connectedto implant 470, this embodiment functions like a pulley in that atensioning force applied to one end of line 438 is magnified as ispasses through the passages 474. As such, greater force can be used tosecure the implant without increasing the load on line 438.

Furthermore, by connecting line 438 to implant 470 at two spaced apartlocations the implant is secured in a more stable configuration thatprevents unwanted sliding or rotation on the bone. In other embodiments,it is appreciated that line 438 can be connected to only a singleprojection 474. It is also appreciated that a first line can beconnected to projection 474A while a second line is connected toprojection 474B. In like manner, it is appreciated that in allembodiment disclosed herein, two or more discrete lines can be connectedtwo each of the implants using any of the methods disclosed herein. Itis also appreciated that there are still a large number of other ways inwhich line 438 can be secured to an implant. For example, the line canbe welded, press fit, or attached by a variety of different types offasteners such as bolts, rivets, or clamps. Examples of still othercondylar implants having a line connected thereto are also disclosed inthe '941 application.

Depicted in FIG. 15 is one embodiment of an anchor assembly 810 used tosecure condylar implant 300 to tibia 12. Anchor assembly 810 comprises abone anchor 812 that operably connects with a lock 813. As discussedbelow in greater detail, bone anchor 812 is selectively placed by afirst drive 814 while lock 813 is selectively placed by a second driver816.

Turning to FIG. 16, bone anchor 812 comprises a tubular body 818 havinga substantially cylindrical configuration. Body 818 includes an interiorsurface 820 and an exterior surface 821 that each extend between aproximal end 822 and an opposing distal end 823. Distal end 823 tapersto a reduced nose 824. Formed at proximal end 822 is an engaging head827 having an exterior surface with a transverse cross section that ispolygonal or any other non-round configuration. As a result, firstdriver 814 can connect with engaging head 827 to selectively rotate boneanchor 812. Encircling and radially outwardly projecting from exteriorsurface 821 are one or more helical threads 825. Threads 825 can beconventional or self-taping and extend radially outward beyond the outerperimeter of engaging head 827. In alternative embodiments, threads 825can be replaced by ridges, barbs, or other bone engaging structures usedin conventional bone anchors. Bone anchor 825 can be formed of abiocompatible metal, a bioabsorbable polymer, a bioactive ceramic, orany other desired material.

As depicted in FIG. 17, interior surface 820 bounds a channel 826longitudinally extending through bone anchor 812. Extending proximal todistal, interior surface 820 comprises a threaded portion 828, afrustoconical tapered portion 830, and a constricted cylindrical portion833.

Returning to FIG. 16, in the embodiment depicted, lock 813 comprises acollet. In general, lock 813 has a proximal end 836, an opposing distalend 838, and a channel 840 extending therebetween. More specifically,lock 813 comprises a tubular body 846 extending from proximal end 836 toa second end 850. Encircling and radially, outwardly projecting frombody 846 are one or more helical threads 852. Threads 852 are configuredto engage with threaded portion 828 of bone anchor 812. At least aportion of channel 840 extending through body 846 is bounded by aninterior surface 847 having a polygonal or other non-circular transversecross section so that second driver 816 (FIG. 15) can be secured thereinfor selective rotation of lock 813.

Projecting from second end 850 of body 846 are a plurality of flexiblefingers 856. As depicted in FIG. 18, four finger 856 are provided witheach finger 856 being separated by a slot 857 extending along the lengthof fingers 856. In alternative embodiments, two or more fingers 856 canbe used. The distal end of each finger 856 is radially, inwardlytapered.

As depicted in FIG. 19, during operation lock 813 is partially screwedinto proximal end 822 of bone anchor 812. In this position, with fingers856 unflexed, line 438 is passed through channels 826 and 840. Asdiscussed below in greater detail, when it is desired to secure line 438relative to bone anchor, lock 813 is advanced further into bone anchor812 until tightly secured therein. In so doing, fingers 856 of lock 813bias against tapered portion 830 of bone anchor 812 which causes fingers856 to radially, inwardly constrict and securely engage line 438. Inthis position, line 438 is prevented from being pulled in eitherdirection. However, line 438 can again be freely moved by simplyunscrewing lock 813 from within bone anchor 812 so that fingers 856 areable to freely, outwardly flex.

Returning to FIG. 15, first driver 814 comprises a tubular shaft 862having a proximal end 863 and an opposing distal end 864. A handle 865is formed at proximal end 863. A passage 866 extends through shaft 862and handle 865 so that line 438 can pass completely through first driver814. Passage 866 at distal end 864 has an interior surface that iscomplementary to the exterior surface of engaging head 827 of boneanchor 812. As such, first driver 814 can be selectively coupled withbone anchor. 812 for selective rotation of bone anchor 812.

Second driver 816 also comprises a tubular shaft 867 having a proximalend 868 and an opposing distal end 870. A tubular handle 872 is mountedproximal end 868. As such, a passage 874 extends the length of seconddriver 816 so that line 438 can extend completely therethrough. Distalend 870 of shaft 867 terminates at a tip 875. Tip 875 has aconfiguration complementary to channel 840 at proximal end 836 of lock813. As such, second driver 816 can be selectively coupled with lock 813for selective rotation of lock 813.

Turning to FIG. 20, to facilitate mounting of condylar implant 300, withthe second end of line 438 connected to implant 300, first end 439 ofline 438 is passed through tunnel 400 from second end 404 (FIGS. 3 and4) to first end 402. In one embodiment this is accomplished by passingan instrument up through tunnel 400 from first end 402 to second end404. The instrument is then used to grab first end 439 of line 438 andpull it down through tunnel 400. Other techniques can also be used.

Line 438 is continually pulled through tunnel 400 to remove all slack.With the slack removed, condylar implant 300 is slid onto resectedsurface 234 so as to fit within pocket 194. Here it is noted thatbecause condylar implant 300 has a relatively low profile, condylarimplant 300 can be easily passed through the relatively small incisionthat was originally formed over the medial meniscus. This is in contrastto other conventional procedures where larger incisions must be made toeither allow placement of an implant having a large stem that isembedded within the bone for securing or to provide access room toenable securing the implant by passing screws down through the top of atleast a portion of the implant.

Once implant 300 is positioned, bone anchor 812 is fed onto line 438.Specifically, with lock 813 partially inserted into bone anchor 812, asdiscussed above with reference to FIG. 19, first end 439 of line 438 ispassed distal to proximal through channels 826 and 840 of bone anchor812 and lock 813. First end 439 of line 438 then is passed distal toproximal through passage 866 of first driver 814 so that first driver814 can removably couple with bone anchor 812. It is appreciated thatthe above steps can be performed in a variety of different sequences.For example, line 428 can be passed through bone anchor 812 and lock 813separately before they are connected together.

First driver 814 is then used to screw bone anchor 812, having lock 813therein, into first end 402 of tunnel 400. Bone anchor 812 is advanceduntil proximal end 822 passes into tibia 12. In one embodiment, a tap,not shown, is used to initially thread the interior surface of tunnel400 at first end 402. Alternatively, bone anchor 812 can beself-tapping.

Next, a tensioner 878 is used to tension line 438. As depicted in FIGS.21 and 22, tensioner 878 comprises a frame 880 having a proximal end 881and an opposing distal end 882. Distal end 882 removably connects tohandle 865 of fist driver 814. A channel 884 is formed within a portionof frame 880. Rotatably disposed within channel 884 is a threaded shaft886. A portion of shaft 886 extends beyond proximal end 881 and has ahandle 888 connected thereto. Mounted on threaded shaft 886 withinchannel 884 is a clamp arm 890. Clamp arm 890 is mounted such thatrotation of shaft 886 by rotation of handle 888 causes clamp arm 890 toselectively advance along shaft 886 depending on the direction ofrotation.

Positioned on clamp arm 890 is a stop plate 892. An eccentricallymounted cam 894 is rotatably mounted to clamp arm 890 and is springbiased against stop plate 892. A handle 895 projects from cam 894.Depressing handle 895 causes cam 894 to rotate away from stop plate 892.Line 438 can then be placed between cam 894 and stop plate 892. Whenhandle 895 is released, cam 894 spring biases against stop plate 892causing line 438 to be secured therebetween. Because cam 894 iseccentrically mounted, the more tension on line 438 toward first driver814, the greater the force applied by cam 894 to secure line 438 inplace.

Turning to FIG. 23, once bone anchor 812 has been mounted to tibia 12,first end 439 of line 438 is passed distal to proximal through passage874 in second driver 816. Proximal end 870 of second driver 816 is thenadvanced proximal to distal through passage 866 of first driver 814.Second driver 816 is advanced until distal tip 875 couples with lock813. Next, tensioner 878 is connected with handle 865 of first driver814. Line 438 extending from second driver 816 is then connected toclamp arm 890 by cam 894 as discussed above. Handle 888 of tensioner 878is then rotated so that clamp arm 890 is moved along threaded shaft 886away from second driver 816. In so doing, a tension force is applied toline 438.

A force measuring device, such as a transducer, can be coupled withtensioner 878 for measuring the tension force applied to line 438. Inturn, the tension force on line 438 is the same force used to biasimplant 300 against tibia 12. When a sufficient tension force is appliedto line 438, handle 872 of second driver 872 is rotated, thereby causinglock 813 to secure line 438 within bone anchor 812. In one embodiment,the tension force applied to line 438 is in a range between about 25pounds (110 N) to about 300 pounds (1,335 N) with about 150 pounds (670N) to about: 250 pounds (1,110 N) being more common. Other forces canalso be applied.

Once lock 813 is secured in place, tensioner 878, second driver 816 andfirst driver 814 are removed. One of the unique features of thisembodiment of the present invention is that should the surgeon wish tomake some modification to the implant or related anchor system, lock 813can simply be loosened using second driver 816 to allow the desiredmovement or adjustment. The above process can then be repeated toresecure implant 300 in place. Once properly position and secured, line438 is severed just proximal of lock 813. Even after line 438 issevered, however, further tension can be applied to line 438 by backingbone anchor 812 back toward first end 402 of tunnel 400 using firstdriver 814. Closing procedures for the tissue are then performed.

It is appreciated that many of the mounting steps can be modified orperformed in an alternative order. For example, in one method condylarimplant can be positioned in pocket 194 prior to having line 438connected thereto. As previously discussed with regard to FIG. 5, adriver can then be used to secure line 438 to implant 300 by passingretainer 444 through tunnel 400 from first end 402 to second end 404where retainer is then screwed into implant 300, thereby securing line438 to implant 300.

In one embodiment of the present invention means are also provided forsecuring line 438 to bone anchor 812. One example of such meanscomprises lock 813. In alternative embodiments lock 813 can have avariety of different configurations or be replaced with a variety ofdifferent structures. For example, any number of different wedges,cleats, or cams can be placed in bone anchor 812 so that line 438 can bepulled one way through bone anchor 812 but is prevented from beingpulled back. In yet other embodiments, once line 438 is tensioned, alock can be crimped or otherwise secured to line 438. The lock wouldthen bias against bone anchor 812 to prevent line 438 from: beingpulling back through bone anchor 812. Examples of various locks whichcan be used are disclosed in U.S. Pat. No. 5,702,397, issued Dec. 30,1997 and U.S. patent application Ser. No. 09/970,559, filed Oct. 3,2001. The bone anchors with related line locking structures disclosed inPat. No. 5,702,397 and application Ser. No. 09/970,559 are incorporatedherein by specific reference.

In still other embodiments, it is appreciated that bone anchor 812 canhave a variety of different configurations. For example, depicted inFIGS. 24A and 24B are alternative bone anchors 980A and B, respectively.Like elements between the different bone anchors are identified by likereference characters. Each of bone anchors 980A and B is tubular havingchannel 826 extending therethrough. Likewise, threaded portion 828 andtapered portion 830 (FIG. 17) are formed within each channel 826. Incontrast to the polygonal engaging head 827 of bone anchor 812, boneanchor 980A has an enlarged, rounded head 982 formed at proximal end822. Head 982 has a maximum outer diameter larger than the maximum outerdiameter of threads 825. In an alternative embodiment, threads 825 canextend the full length of bone anchor 980A. To facilitate engagement ofbone anchor 980A with a driver, a polygonal socket 984 is formed atproximal end 822.

Bone anchor 980B is similar to bone anchor 980A except that helicalthreads 825 have been completely removed. In this embodiment, exteriorsurface 821 extending between proximal end 822 and distal end 823 issmooth. Bone anchor 980B is designed to be slid or wedged within thebone tunnel and held in place by the taper along the length thereofand/or the enlarged head 982. By increasing the exterior taper of boneanchor 980B, it is also appreciated that enlarged head 982 can beremoved. Because bone anchor 980B is not threaded into the bone, socket430 at proximal end 416 need not be polygonal to engage a driver but canbe round. In alternative embodiment, the interior or exterior surface ofhead 982 can have a polygonal or other non-circular configuration so asto facilitate positive engagement with a driver.

Depicted in FIG. 25 is one embodiment of a system used for mountingimplant 470 as previously discussed with regard to FIG. 14. In thisembodiment, two a tunnels 400A and 400B extend from lateral side 14 oftibia 12 to resected surface 234. Tunnels 400A and B can be formedhaving parallel alignment or any desired angle.

To secure implant 470 to tibia 12, first end 439 of line 438 is passedproximal to distal through channel 826 in first bone anchor 812A. Firstend 439 is then passed up through first tunnel 400A, though passages 475on implant 470 (FIG. 14), down through second tunnel 400B, and finallythrough second bone anchor 812B and lock 813. First driver 814 is usedto drive bone anchors 812A and B into corresponding tunnels 400A and B.Line 438 is pulled down through second tunnel 400B so as to remove theslack therefrom. In so doing, enlarged head 442 on second end 440 ofline 438 is advanced into first bone anchor 812A where head 442 issecurely wedged within tapered portion 830 of channel 826 (FIG. 17).With second end 440 of line 438 secured to bone anchor 812A, the sameprocess previously discussed with regard to FIG. 23 is used tension line438 and secure line 438 to second bone anchor 812 using lock 813.

It is appreciated that first bone anchor 812A can be replaced with avariety of alternative structures that prevent second end 440 of line438 from being pulled through first tunnel 400A. For example, the firstbone anchor can simply comprise an enlarged washer that capturesenlarged head 442 but is too big to pass through tunnel 400A. In yetother embodiment, the first bone anchor can simply comprise an enlargedtubular wedge that wedges into tunnel 400A but cannot pass therethrough.In still other embodiments, line 438 can be formed without enlarged head442. In this embodiment, lock 813 or other wedging or locking typestructure can be used to secure second end 440 of line 438 to the firstbone anchor. Where two separate lines 438 are connected to an implant,each line is extended through a corresponding tunnel. The processdiscussed with regard to FIG. 23 is then separately performed for eachseparate line.

Line 438 and anchor assembly 810 is one embodiment of means for securingan implant to a bone. It is appreciated, however, that other anchoringtechniques can also be used. For example, another system for securing animplant to a bone is disclosed in U.S. patent application Ser. No.10/798,665, filed Mar. 11, 2004 which is incorporated herein by specificreference.

By using the above discussed implants and anchor assemblies with thecorresponding methods and instruments, it is appreciated that theimplants can be securely mounted to tibia 12 using procedures that areminimally invasive. Furthermore, because the implants are only securedin place after they are positioned on the proximal end of the tibia, thesurgeon can easily switch out different sizes of implants when trying todetermine an appropriate fit. Likewise, because the anchoring assembliesare operated through the first end of the tunnel which is remote fromthe implant, the inventive anchoring assemblies enable the surgeon toeasily adjust the placement of the implant during initial positioningand to subsequently remove the implant should a replacement be requiredat a later date.

Furthermore, as a result of using a flexible line to secure theimplants, the surgeon can select the best location for forming thetunnel and mounting the bone anchor at the time of the operation. Thatis, the surgeon is not limited to forming the tunnel at a predefinedlocation based on structural limitations imposed by the implant. Inaddition, because the line can be relatively small, the size of therequired tunnel can be minimized, thereby minimizing the amount of bonethat needs to be removed when forming the tunnel. Replacement of a wornor damaged implant is also relatively easily achieved by cutting theline.

Because the inventive implants, anchor assemblies, tissue preparationinstruments, and corresponding methods each produce independently uniquebenefits, it is appreciated that theses various features can be usedindependently with other conventional apparatus and techniques. Forexample, in one embodiment a larger incisions can be made at the knee ofa patient and the proximal end of tibia 12 resected using conventionalresection techniques. In this embodiment, tunnel 400 can be formedeither before or after the resection of tibia 12. Once the tibia isresected and the tunnel formed, the above procedure can then be used tosecure condylar implant 300. In another alternative, tunnel 400 can beformed and tibia 12 resected as discussed above. However, once tibia 12is resected, a conventional implant can be mounted on tibia 12 usingconventional techniques.

The above discussed embodiments relate to mounting a condylar implant ontibia 12. As previously mentioned, however, the present invention canalso be used to mount other types of implants on other articulationsurface so as to achieve one or more of the same benefits. For example,the '941 application also discloses a full tibial implant and methodsfor mounting.

Features of the present invention can also be used for mounting afemoral implant on the distal end of a femur. Like elements betweendifferent embodiments are identified by like reference characters. Forexample, depicted in FIG. 45 is a distal end 532 of a femur 530 having amedial side 540 and a lateral side 542 that extend between an anteriorside 538 and a posterior side 536. Distal end 532 of femur 530terminates at a lateral condyle 535 and a medial condyle 537 with atrochlear groove 539 disposed therebetween.

Mounted on medial condyle 537 is a guide template 900. Guide templatebounds an elongated opening 902 that extends therethrough and which isconfigured to closely fit over a predefined portion of an articulationsurface of medial condyle 537. Opening 902 bounds the area where thebone is to be resected and a condylar implant mounted. Guide template iscurved and comes in a variety of different sizes and shapes so that aproper fit can be made on medial condyle 537. Once a proper sized andfitting guide template 900 is positioned, guide template 900 is securedin place by spaced apart screws 904 that are screwed through mountingholes in guide template 900 and into the medial side of femur 530.

In one embodiment, a milling head 906 is used to facilitate resection ofmedial condyle 537 bounded by guide template. Milling head 906 has asubstantially hour-glass configuration and has an elongated handle 908projecting from one side and a stem 909 projecting from the other.Milling head 906 is positioned within opening 902 in a medial-lateralorientation with handle 908 projecting from medial side 540 of femur530. In this orientation, milling head 906 is rapidly rotated and thenselectively moved within opening 902 anterior-posterior. This movementis guided by the sides of guide template 900 bounding opening 902.Milling head 906 grinds away the bone bounded within opening 902 untilhandle 908 and stem 909 rest against guide template 900, therebypreventing milling head 906 from descending further into the bone.

Because guide template 900 is curved anterior-posterior, the milledpocket formed by milling head 906 is outwardly archedanterior-posterior. Likewise, because milling head 906 is curvedlateral-medial, the milled pocket is also outwardly archedlateral-medial. As such, the recessed pocket produced by milling head906 is arched anterior-posterior and lateral-medial. Again, this pocketconfiguration enables the formation of a low profile implant havingsubstantially uniform thickness and strength. Furthermore, the pocketformation produces a stable platform for the implant having acomplementary configuration. In alternative embodiments, it is againappreciated that milling head 906 can have a variety of differentconfigurations.

As depicted in FIG. 27 and 28, a rasp 910 can be used to form roundedends for the recessed pocket. Rasp 910 comprises an elongated handle 912having a cutting mount 913 mounted on the end thereof. Cutting mount 913has a generally semi-circular transverse cross section with a concavecutting surface 914. Formed on cutting surface 914 are a plurality ofcutting teeth 915. Extending through cutting mount are a plurality ofslots through which bone fragments can be removed. Cutting mount 913 isconfigured to be reciprocally moved within the opposing ends of opening902 of guide template 900 so as to form rounded ends on the pocketformed to receive the implant.

Once the recessed pocket is finished, a tunnel guide can be used to formtunnel 400 extending from lateral side 542 of femur 530 to the recessedpocket. Examples of such tunnel guides and corresponding method of useare disclosed in the '941 application. Alternatively, tunnel 400 can bedrilled starting at the recessed pocket and extending to the lateral ormedial side of the femur. Because it is less critical where tunnel exitson the lateral or medial side, a tunnel guide is not required but could,if desired, still be used. This process can also be used on the tibialside.

Once tunnel 400 is formed, a femoral condylar implant 928 is thenpositioned within the recessed pocket. As depicted in FIGS. 29 and 30,in one embodiment femoral condylar implant 928 comprises an elongatedbody 930 having a first side 500 and an opposing second side 502 thatextends between opposing ends 504 and 506. Body 920 also has a curvedarticular surface 931 and an opposing bottom surface 932. In oneembodiment, articular surface 931 can have a continuous convex curvaturewhich extends between opposing sides 500 and 502 and a continuous convexcurvature which extends between opposing ends 504 and 506.

A pair of pockets 934 A and B are formed on bottom surface 932 and areseparated by a bridge 935. Disposed within each pocket 934A and B is aninlay 936A and B of porous bone ingrowth material. Bridge 935 and inlays936A and B substantially comprise a bone apposition surface 938. Boneapposition surface 938 can have a configuration complementary to theformation of the recessed pocket formed on medial condyle 537. Boneapposition surface 938 can also have a configuration complementary toarticular surface 931. In one embodiment, bone apposition surface 938can have a continuous concave curvature which extends between opposingsides 500 and 502 and a continuous concave curvature which extendsbetween opposing ends 504 and 506. As a result, condylar implant canhave a substantially uniform thickness along its length.

Connected to bridge 935 is line 438. It is appreciated that the variousalternatives as previously discussed with regard to the tibial condylarimplants and the methods for connecting line 438 thereto are alsoapplicable to femoral condylar implant 928.

Finally, turning to FIG. 31, femoral condylar implant 928 is secured tofemur 530 using anchor assembly 810 (FIG. 15) and the instruments andtechniques as previously discussed with regard to FIGS. 15-25. The samealternatives as previously discussed with regard to FIGS. 15-25 are alsoapplicable to the attachment of femoral condylar implant 928. Forexample, two separate tunnels can be formed on femur 530 that intersectwith the recessed pocket on medial condyle 537. Opposing ends of asingle line 438 slidably connected to implant 928 can be passed throughthe separate tunnels and secured with corresponding bone anchors.Alternatively, two separate and discrete lines 438 can be connected tofemoral condylar implant 928, each line being disposed in a separatetunnel.

The present invention can also be used for mounting a trochlear implanton femur 530. For example, depicted in FIG. 32 is a guide template 950incorporating features of the present invention. Guide template 950 ismounted on distal end 532 of femur 530 so as to be disposed over atleast a portion of trochlear groove 539. As depicted in FIGS. 33 and 34,guide template 950 comprises a body 952 having a top surface 954 and anopposing bottom surface 956. Body 952 also has a proximal end 958 and anopposing distal end 960 which each extend between opposing sides 962 and964. Top surface 954 has a convex arch or curve that extends betweenopposing ends 958 and 960 while bottom surface 956 has a concave arch orcurve that extends between opposing ends 958 and 960.

Extending through body 952 between top surface 954 and bottom surface956 is an enlarged opening 966. Opening 966 is configured to overlay thebone which is to be removed so as to form a pocket in which thetrochlear implant is received. The portion of the bone that is removedincludes all or a portion of the bone forming trochlear groove 539 and,optionally, additional surrounding bone. In one embodiment, opening 966has or covers an area in a range between about 3 cm² to about 20 cm²with about 9 cm² to about 16 cm² being more common. Other dimensions canalso be used.

It is appreciated that opening 966 can have a variety of differentconfigurations. In the embodiment depicted, opening 966 is bounded by aninterior surface 968. As perhaps best depicted in FIG. 32, interiorsurface 968 comprises two substantially linear side section 972 and 974that extend between opposing ends 958 and 960 in substantially parallelalignment. A linear proximal section 970 extends between sides sections972 and 974 at proximal end 958. An arched distal section 976 extendsbetween side sections 972 and 974 and distal end 960. Distal section 976is asymmetrically arched. As such opening 966 has an asymmetricalconfiguration. This asymmetry is a result of the irregular anatomicalconfiguration of distal end 932 of femur 530. In alternativeembodiments, anterior section 970 can also be arched. Furthermore, instill other embodiments arched posterior section 976 can by symmetrical.

Turning again to FIG. 34, downwardly projecting from bottom surface 956of body 952 are three spaced apart supports 978, 979, and 980. Supports978 and 979 are located at or toward distal end 960 while support 980 islocated at or toward proximal end 958. Supports 978, 979, and 980 areconfigured to support body 952 off of femur 530. Specifically, asdepicted in FIG. 32, body 952 is supported on femur 530 as a result ofsupport 978 resting against medial conidial 937, support 979 restingagainst lateral conidial 535, and support 980 resting against anteriorside 538, such as within or adjacent to trochlear groove 539.

Because the area surrounding trochlear groove 539 has an irregularconfiguration, the use of three supports 978-980 provides a stableplatform that can be easily designed so as to rest in a stable fashionon a plurality of differently sized and shaped femurs. In alternativeembodiments, it is appreciated that the supports can be positioned atdifferent locations on body 952 and can have a variety of differentsizes and shapes. Furthermore, fewer or more supports can also be used.For example, guide template 950 can be designed with two supports sothat the two supports and a portion of body 952 rest directly againstfemur 930. In yet other embodiments, four or more supports can be formedprojecting from body 952.

As depicted in FIGS. 32 and 33, upwardly projecting from top surface 954of body 952 is an elongated first guide rail 982 and an elongated secondguide rail 984. First guide rail 982 upwardly extends from side 962while second guide rail 984 upwardly extends from side 964. Guide rails982 and 984 extend between opposing ends 958 and 960 in substantiallyparallel alignment and are formed so that a portion of the top surface952 is openly exposed between each of the guide rails and opening 966.As will be discussed below in greater detail, this portion of topsurface 952 is designed for engagement with a rasp. A catch 986 alsoupwardly projects from top surface 954 at distal end 960.

The present invention also includes means for securing body 952 to femur530. By way of example and not by limitation, spaced apart mountingholes 988 are formed on or extend through body 952. Screws 990 or otherfasteners can be passed through mounting holes 988 so as to secure guidetemplate 950 to femur 930 once guide template 950 is positioned in thedesired location. In the embodiment depicted, three mounting holes andscrews are used to secure guide template 950. As in prior embodiments,however, alternative numbers of screws and mounting holes or other typesof fastening techniques can also be used. Furthermore, the mountingholes 988 can be positioned at a variety of different locations on body952 and can have a variety of different orientations so as to betterstabilize body 952 when the screws are received therein. Likewise,mounting holes 988 are positioned and oriented so that screws 990 onlyenter the bone outside of the articulation surface, i.e., articularcartilage or on a non-function peripheral edge thereof.

Turning to FIG. 35, once guide template 950 is secured in place, a rasp994 is used to facilitate resection of the portion of femur 932 boundedby opening 966. As depicted in FIGS. 36-38, rasp 994 comprises anelongated handle 996 having a top surface 998 and an opposing bottomsurface 1000 each extending between a first end 1002 and an opposingsecond end 1004. Mounted at second end 1004 is a head 1006. Head 1006comprises an elongated slide rest 1008 having a contact surface 1010extending between a first end face 1012 and an opposing second end face1014.

Projecting from contact face 1010 of slide rest 1008 is a cutting mount1016. Cutting mount 1016 comprises a cutting surface 1018 formed by aplurality of cutting teeth 1020. (It is noted that in FIGS. 38, 39, 41,51 52, and 58 that cutting teeth 1020 have been removed for ease inillustration.) A plurality of channels 1022 extend through cutting mount1016 and facilitate removal of bone fragments that are resected by arasp 994. As shown in FIG. 37, cutting mount 1016 has a proximal end1024 and an opposing distal end 1026 which each extend between opposingsides 1028 and 1030. The distance between opposing sides 1028 and 1030is substantially equal to the width of opening 966 of guide template950. Turning to FIG. 39, distal end 1026 is generally linear and iscomplementary to proximal section 970 of body 952 bounding opening 966.Likewise, proximal end 1024 is asymmetrically arched and iscomplementary to distal section 976 of body 952 bounding opening 966.

As depicted in FIGS. 37 and 38, cutting surface 1018 comprises arounded, outwardly projecting ridge 1032 that extends between proximalend 1024 and distal end 1026 at a location substantially central betweenopposing sides 1028 and 1030. Furthermore, as depicted in FIG. 36,cutting surface 1018, including ridge 1032, is curved along itslongitudinal axis in a concave arch that curves away from handle 996.This figure also shows ridge 1032 having an apex extending along thelength thereof having a concave arch.

During operation as depicted in FIG. 35, cutting mount 1016 of rasp 994is received within opening 966 of guide template 950 such that opposingside faces 1012 and 1014 of slide rest 1008 are disposed between andadjacent to guide rails 984 and 982, respectively. The interactionbetween guide rails 984, 982 and slide rest 1008 limits and guides themovement of cutting mount 1016 in a linear path between the opposingends of opening 966. First end 1002 of handle 996 is coupled with areciprocating driver so to facilitate rapid reciprocating of cuttingmount 1016 within opening 966. Reciprocating cutting surface 1018 ofcutting mount 1016 against the portion of femur 530 bounded by opening966 progressively removes the bone by rasping. As the bone isprogressively removed by teeth 1020, cutting mount 1016 continues todescend within opening 996 until the opposing ends of slide rest 1008rest against top surface 954 of body 952 on opposing sides of opening966.

Once slide rest 1008 reaches top surface 954, the bone has been removedto the desired depth. Here it is noted that the curvature of top surface954 causes rasp 994 to move in a curved path as slide rest 1008 slidesalong top surface 954. Rasp 994 is then removed so as to reveal, asdepicted in FIG. 40, a recessed pocket 942. Pocket 942 is bounded by afloor 944 having an encircling side wall 946 upstanding around theperimeter thereof. Pocket 942 has opposing sides 949 and 951 that extendbetween a proximal end 953 and an opposing distal end 955.

Due to the configuration of cutting mount 1016, a rounded, elongatedchannel 948 is recessed along floor 944 in substantial alignment withwhere trochlear groove 539 was previously disposed. That is, channel 948extends between opposing ends 953 and 955. Floor 944 also has a convexcurvature that extends between opposing ends 953 and 955. As will bediscussed below in greater detail, the configuration of recessed pocket942 enables the formation of a low profile trochlear implant havingsubstantially uniform thickness. Furthermore, the formation of pocket942 produces a stable platform for the implant having a complementaryconfiguration.

In one alternative embodiment, it is appreciated that recessed pocket942 can be formed by using two or more different rasps. For example,instead of trying to remove all of the bone material using a singlerasp, a smaller rasp can initially be used to form channel 948 withinrecessed pocket 942. By way of an illustrated example, depicted in FIGS.41A and 41B are cutting head 1006, as previously discussed, and acutting head 1006A, respectively. Cutting head 1006A comprises sliderest 1008 and a cutting mount 1016A projecting therefrom. Cutting mount1016A is substantially the same as cutting mount 1016 except thatcutting surface 1018 has been resected on each side of ridge 1032. As aresult, cutting head 1006A can initially be used to form channel 948 ofrecessed pocket 942. Cutting head 1006 can then be used to remove therest of the bone so as to form recessed pocket 942. It is appreciatedthat any number of different rasps can be configured to removeddifferent portions of recessed pocket 942.

Depicted in FIG. 42 is another alternative embodiment of a rasp 1034incorporating features of the present invention. Rasp 1034 compriseshandle 996 as previously discussed and a cutting head 1036 mounted onthe end thereof. Cutting head 1036 comprises a cutting mount 1038 havinga cutting surface 1040 comprised of a plurality of cutting teeth 1042.Cutting surface 1040 has a proximal end 1044 and an opposing distal end1046 which each extend between opposing side faces 1048 and 1050. (Forease in illustration, cutting teeth 1042 have only been depicted on thecentral portion of cutting surface 1040. Cutting teeth actually extendover all of surface 1040 between side faces 148 and 1050.) In oneembodiment, opposing ends 1048 and 1046 have a length in a range betweenabout 1.5 cm to about 6 cm with about 2 cm to about 4 cm being morecommon. Other dimensions, however, can also be used. Outwardlyprojecting from each side face 1048 and 1050 is a corresponding sliderest 1052. In this embodiment, each slide rest 1052 rounded, such as byhaving a substantially cylindrical configuration.

Cutting surface 1040 substantially comprises a surface of rotation whichcurves between proximal end 1044 and distal end 1046 about a commonrotational axis 1056. Of course, the surface of rotation has somevariation due to the fact that it is formed from the plurality of teeth1042. In one embodiment, cutting surface 1040 can extend about axis 1056over an angle greater that 300°. More commonly however, cutting surface1040 extend over an angle in a range between about 15° to about 180°with about 25° to about 100° being more common. Other angles can also beused.

Cutting surface 1040 is also depicted as having a non-linear contourwhen viewed in a plane extending between side faces 1048 and 1050 andintersection with rotational axis 1056 along the length thereof.Specifically, cutting surface 1040 has a rounded, outwardly projectingridge 1054 which extends between opposing ends 1044 and 1046substantially centrally between opposing side faces 1048 and 1050. Ridge1054 is used to form channel 948 of recessed pocket 942. It isappreciated that rasp 1034 can be used to form recessed pockets forother types of implants and that in such alternative uses, the contourof cutting surface 1040 can have a variety of different configurations.

Rasp 1034 is configured so that cutting mount 1038 can be disposedwithin opening 966 of guide template 950 so that as rasp 1034 isreciprocated, cutting surface 1040 reciprocates against the bonesurface. In turn, teeth 1042 on cutting surface 1040 progressivelyresect the bone surface until slide rests 1052 bear against top surface954 of guide template 950. Rasp 1034 can thus also be used to formrecessed pocket 942 having channel 948. One of the benefits of rasp 1034is that because of the unique configuration of cutting surface 1040,cutting surface 1040 can be rotated or positioned at any desired angleabout axis of rotation 1056 and still produce recessed pocket 942 havingthe same contour. As a result, the operator of rasp 1034 is able toselectively position or repeatedly position the orientation of handle996 for the most convenient orientation of reciprocating withoutjeopardizing the desired configuration for recessed pocket 942.

During the rasping process, it is noted that the rasp can cause slightvibration or movement of guide template 950 which is typically formedfrom a metal or other rigid material. In turn, this movement can causesupports 978 and 979, which are typically integrally formed with body952, to wear against the articulation surface. To prevent unwanted wear,flexible pads can be positioned between supports 978 and 979 and thearticulation surface. In other embodiments, all or portions of thesupports 978 and 979 can be formed from a flexible material that willnot damage the articulation surface. Such flexible materials cancomprise a polymeric or rubber material. In yet other embodiments asdiscussed below in greater detail, the supports can be removed duringthe rasping process to as to avoid damage to the articulation surface.

Once recessed pocket 942 is finished, the rasp is removed and tunnel 400is formed extending from pocket 942 to a location spaced apart from thearticulation surface, such as the lateral or medial side of femur 530.As disclosed in various embodiments depicted in the '941 application,guide template 950 can be used in association with a centering templateand tunnel guide to facilitate formation of tunnel 400. In analternative embodiment, it is again appreciated that the centeringtemplate and tunnel guide can be eliminated. That is, tunnel 400 can bedrilled after removal of guide template 950 by starting at recessedpocket 942 and extending to the lateral or medial side of the femur 530.Because it is less critical where tunnel exits on the lateral or medialside, a tunnel guide is not required but could, if desired, still beused.

Once tunnel 400 is formed, a trochlear implant is then secured withinthe recessed pocket 942. Depicted in FIGS. 43 and 44 is one embodimentof a trochlear implant 1064 incorporating features of the presentinvention. Trochlear implant 1064 comprises a body 1066 having anarticular surface 1068 and an opposing bottom surface 1070 that eachextend to a perimeter edge 1071. Body 1066 is further defined as havingan proximal end 1072 and a distal end 1074 each extending between alateral side 1076 and a medial side 1078. Articular surface 1068 isformed having an elongated channel 1080 extending between proximal end1072 and distal end 1074 substantially centrally between sides 1076 and1078. Channel 1080 forms a least a portion of the resurfaced trochleargroove in which the patella rides.

In one embodiment viewed in a plane extending between sides 1076 and1078 (FIG. 43A), channel 1080 has a bottom 1081 with a concavecurvature. The surfaces extending from the concave curvature at bottom1081 to perimeter edge 1071 at each side 1076 and 1078 are typically notconcave. Rather, these surfaces are typically substantially flat so asto form a substantially V-shaped transverse cross section with roundedbottom or have a substantially convex curvature. It is also appreciatedthat articular surface 1068 has a smooth continuous convex curvaturethat extends between opposing ends 1072 and 1074.

Depicted in FIG. 44, formed on bottom surface 1070 is a pocket 1082. Itis appreciated that flexible line 438 can be secured to trochlearimplant 1064 using any of the techniques previously discussed. In theembodiment depicted, a post 1084 projects from within pocket 1082. Aconstricting passage 1086 extends through post 1084 and is configured tohold flexible line 438 such as previously discussed. Secured withinpocket 1082 is an inlay 1088 of a porous bone ingrowth material. Inlay1088 has an opening 1090 formed thereon through which post 1084 extends.

As depicted in FIG. 45, bottom surface 1070 and inlay 1088 combine toform a bone apposition surface 1092 of trochlear implant 1064. Boneapposition surface 1092 has a configuration complementary to theformation of the recessed pocket 942 formed on femur 530. Boneapposition surface 1092 also typically has a configuration complementaryto articular surface 1068. Specifically, bone apposition surface 1092 isformed having a rounded, outwardly projecting ridge 1094 that extendsbetween proximal end 1072 and distal end 1074, substantially centrallybetween sides 1076 and 1078. When viewed in a plane extending betweensides 1076 and 1078 (FIG. 43A), ridge 1094 terminates at an apex 1095having a convex curvature. The side surfaces of ridge 1094 extending tosides 1076 and 1078 are typically substantially flat or have a concavecurvature.

Ridge 1094 is typically aligned with channel 1080 so that trochlearimplant 1064 can have a substantially uniform thickness. For example, inone embodiment bone apposition surface 1092 can be substantiallycomplementary to articular surface 1068 so that implant 1064 has asubstantially uniform thickness between surfaces 1068 and 1092. In otherembodiments, implant 1064 may be slightly tapered along perimeter edge1071. Thus, at all locations at least 2 mm in from the perimeter edge1071, body 1066 has a thickness extending between the bone appositionsurface 1092 and the articular surface 1068 that does not vary by morethan 30%, 20%, or more commonly 15%. Other percentages can also be used.The actual thickness depends on the desired implant and is typically ina range between about 3 mm to about 10 mm.

Ridge 1094 is also configured to be complementarily received withinchannel 948 formed on recessed pocket 942. Bone apposition surface 1092thus also has a continuous concave curvature extending between opposingends 1072 and 1074. Because of the unique method in which pocket 942 canbe formed, bone apposition surface 1092 can be formed having a smoothsurface with no stepped shoulders or corners as required in manyconventional implants. Implant 1064 can also be modified in the samemanner as the other implants disclosed herein. For example, spikes orother forms of projections can be formed projecting from bone appositionsurface 1092.

Because implant 1064 is configured to fit within pocket 942, implant1064 has an outer perimeter having an asymmetrical configuration. In oneembodiment, articular surface 1068 of implant 1064 has a centroidallocation. Articular surface 1068 has a maximum radius extending from thecentroidal location to perimeter edge and a minimum radius extendingfrom the centroidal location to the perimeter edge, the minimum radiusnot being less than 70% and more commonly not being less than 80% of themaximum radius. Other dimensions can also be used. It is alsoappreciated that the alternatives as previously discussed with regard toimplant 300 are also applicable to implant 1064.

Turning to FIG. 46, trochlear implant 1064 is secured within recessedpocket 942 of femur 530 using anchor assembly 810 (FIG. 15) and theinstruments and techniques as previously discussed with regard to FIGS.15-25. The same alternatives as previously discussed with regard toFIGS. 15-25 are also applicable to the attachment of trochlear implant1064. For example, two separate tunnels can be formed on femur 530 thatintersect with the recessed pocket 942. Opposing ends of a single line438 slidably connected to trochlear implant 1064 can be passed throughthe separate tunnels and secured with corresponding bone anchors.Alternatively, two separate and discrete lines 438 can be connected totrochlear implant 1064, each line being disposed in a separate tunnel.Likewise, other means can also be used to secure implant 1064 to femur530 such as those disclosed in U.S. patent application Ser. No.10/798,665 which was previously incorporated by reference.

Depicted in FIG. 47 is an alternative embodiment of a guide template1100 which can be used for forming pocket 942 to receive trochlearimplant 1064. Like elements between guide templates 950 and 1100 areidentified by like reference characters. In contrast to guide template950 where the supports are shown integrally formed with the body, guidetemplate 1100 comprises a modular template. Specifically, guide template1100 comprises a base 1102 and a mount 1104 removable connected to base1102.

Base 1102 comprises body 952, as previously discussed, having support980 projecting from proximal end 958. First guide rail 982 has beeneliminated but second guide rail 984 still upwardly projects from topsurface 952 at side 964. As will be discussed below in greater detail,three mounting holes 988 are formed on side 964 while one mounting hole988 is formed at distal end 960. A coupling hole 1103 (FIG. 49) is alsoformed on body 952 at or toward distal end 960.

As depicted in FIG. 49, mount 1104 comprises a brace 1106 having a frontface 1108 and a back face 1110. Front face 1108 has a contourcomplementary to distal section 976 of body 952. Projecting forward anddown from front face 1108 are supports 978 and 979. A flange 1112 alsoprojects out from brace 1106 and has a coupling hole 1114 extendingtherethrough. As depicted in FIGS. 47 and 48, mount 1104 is removablycoupled with base 1102 by positioning front face 1108 of mount 1104against distal section 976 of body 952 so that supports 978 and 979extend below body 952. In this position, coupling holes 1103 and 1114are aligned. A threaded tip 1118 of a handle 1116 is screwed intocoupling holes 1103 and 1114 so as to selectively secure base 1102 andmount 1104 together. It is appreciated that any number of alternativefastening techniques can be used to selectively secure base 1102 andmount 1104 together.

In the above assembled configuration, guide template 1100 is positionedonto the distal end of femur 530 in substantially the same orientationas previously discussed with regard to FIG. 32. That is, supports 978and 979 are positioned directly on the articulation surface of femur 530so that guide template 1100 is stably supported thereon. A plurality ofguide sleeves and screws or other fasteners are then use to secure guidetemplate 1100 onto femur 530. Specifically, as depicted in FIG. 50,implant 1100 also comprises a tubular guide sleeve 1120 for eachmounting hole 988. Each guide sleeve 1120 comprises a tubular stem 1122having, a first end 1124 and an opposing second end 1126. A passage 1128centrally extends through stem 1122 between opposing ends 1124 and 1126.A circular flange 1130 encircles and radially outwardly projects fromfirst end 1124. Each guide sleeve 1120 is configured so that second end1126 can be received within and slid through a corresponding mountinghole 988. Flange 1130 is larger than mounting hole 988 and thusfunctions as a stop.

Each screw 990 comprises an elongated shaft 1132 having a first end 1134and an opposing second end 1136. Threads 1138 are formed on second end1136 while an enlarged head 1139 is formed at first end 1134. In theembodiment depicted, enlarged head 1139 comprises a flange 1140 thatencircles and radially outwardly projects from first end 1134. Anengagement head 1142 extends above flange 1140 and has a polygonal ornon-circular cross section so that a driver can be connected toengagement head 1142 for selective rotation of screw 990. It isappreciated that enlarged head 1139 of screw 990 can come in a varietyof different configuration. For example, enlarged head 1139 can beformed with a socket, slot(s) or other engaging surfaces to engage withother types of drivers. Each screw 990 is configured so that second end1136 can be received within and slid through a corresponding passage1128 of a guide sleeve 1120. Enlarged head 1139 is larger than passage1128 and thus functions as a stop.

During mounting of guide template 1100, guide template 1100 with mount1104 secured to base 1102 is positioned on the distal end of femur 530in the same orientation as depicted in FIG. 32 so that opening 966 isdisposed over at least a portion of trochlear groove 539. Each guidesleeve 1120 is positioned within a corresponding mounting hole 988either before or after positioning guide template onto femur 530. Aspreviously discussed, supports 978-980 bias against femur 530 so as tosuspend body 952 off of femur 530 and thus off of the articulationsurface. Support 980 is positioned against femur 530 just off of thearticular cartilage but in alignment with the trochlear groove. In thisposition, each guide sleeve 1120 is advanced through the correspondingmounting hole 988 so that the second end 1126 of each guide sleeve buttsagainst the femur 530. Here it is noted that mounting holes 988 arepositioned and orientated so that guide sleeves 1120 and screws 990,which pass therethrough, intersect with femur 530 either adjacent to butoff of the articulation surface or around the perimeter of thearticulation surface. In either event, mounting holes 988 are positionedso that any wear or damage caused by guide sleeves 1120 and screws 990will not detrimentally affect wear or operation of the articulationsurface during normal use of the knee joint.

Furthermore, each mounting hole 988 has a central longitudinal axis 989along with each screw 990 is intended to extend. Mounting holes 988 areoriented at different angles relative to each other so that merelyscrewing screws 990 into femur 530 through guide sleeves 1120 positionedwithin mounting holes 998 causes guide template 1100 to be locked inplace. That is, it is not necessary for screws 990 to directly biasguide template 1100 against femur 530. Due to the off-set angles ofscrews 990 and thus the off-set angles of guide sleeves 1120, it issufficient if screws 990 merely secure guide sleeves 1120 in place tolock guide template 1100 in place.

Once guide sleeves 1120 are properly positioned, screws 990 are passeddown through guide sleeves 1120 and screwed into femur 530. Screws 990are advanced until flange 1140 biases against first end 1124 of eachguide sleeves 1120, thereby securely fixing each guide sleeve 1120 tofemur 530. It is noted that flange 1130 of guide sleeves 1120 need notbias against body 952 bounding mounting holes 988. Flanges 1130primarily function to prevent guide sleeves 1120 from falling throughmounting holes 988 during placement of guide template 1100, and inalternative embodiments flanges 1130 can be eliminated.

In part, guide sleeves 1120 function as guides for screws 990. That is,as a result of supports 978-980, the bottom of the mounting holes 988are spaced above femur 530. This configuration helps ensure properfitting of guide template 1100 without interference by body 952.However, as a result of the spacing between mounting holes 988 and femur530, there is the potential for screws 990 to become misaligned from thecentral longitudinal axis of each corresponding mounting hole 988 as thescrew 990 is passed from mounting hole 988 to femur 530. Thismisalignment can cause binding of the screw 990 against guide template1100 which in turn can cause unwanted displacement or improper securingof guide template 1100. By using guide sleeves 1120 which extend frommounting holes 988 to or adjacent to femur 530, guide sleeves 1120 helpmaintain proper orientation and alignment of each screw 990.

Once all of screws 990 are secured in place so that the guide sleeves1120 are secured in place, guide template 1100 is locked in place. Inthis position, mount 1160 is removed from base 1102 as depicted in FIG.50. This is accomplished by rotating handle 1116 so that tip 1118 isunscrewed from body 952 (FIG. 48). Handle 1116 which is still secured tomount 1160 can then be used to remove mount 1160. As a result, supports978 and 979 are now removed from the articulation surface of femur 530so that distal end 960 of body 952 is freely suspended over thearticulation surface. Again, body 952 is locked in this suspendedorientation by the angled placement of screws 990 and guide sleeves1120. By using modular guide template 1100, this method facilitatesproper positioning of guide template 1100 by using the supports butremoves any structure from directly contacting the functioning portionof the articulation surface prior to rasping so that the articulationsurface is not damaged.

Once mount 1160 is removed, a rasp 1146 as depicted in FIGS. 51 and 52is positioned on body 952 of guide template 1100 so as to selectivelyresect the portion of femur 530 bounded by opening 966, thereby formingrecessed pocket 942 as depicted in FIG. 40. Rasp 1146 is substantiallythe same as rasp 994 in that rasp 1146 includes handle 996 and head 1006which includes slide rest 1008 and cutting mount 1016. However, incontrast to rasp 994, handle 996 is not centrally mounted on head 1006but is mounted toward a side thereof for more convenience during use.Furthermore, a elongated slot 1148 is formed on head 1006 in alignmentwith handle 996. During use, cutting mount 1016 is positioned withinopening 996 so that guide rail 984 is received within slot 1148. Theinteraction of guide rail 984 and slot 1148 thus function as a guide forreciprocating movement of rasp 1146 during the formation of recessedpocket 942. Once pocket 942 is formed, rasp 1146 and guide template 1100are removed. Implant 1064 is then positioned within pocket 942 aspreviously discussed with regard to FIG. 46.

In addition to the other benefits of the present invention previouslydiscussed, the above apparatus and process has other improvements overthe prior art. For example, by using the inventive guide template andrasp, a shallow and precise pocket can be formed to receive the implantwith minimal bone removal. The precise pocket provides for improvedfitting between the implant and the pocket. Minimizing bone removalsimplifies the procedure, minimizes trauma to the bone, and leaves morebone which significantly simplifies subsequent procedures where it maybe necessary to replace the implant or perform: a full arthroplasty.Furthermore, the process allows for smaller, thinner implants which canbe easily mounted and adjusted.

Depicted in FIG. 53 is another alternative embodiment of a guidetemplate 1160 incorporating features of the present invention. Guidetemplate 1160 is used for forming pocket 942 to receive trochlearimplant 1064. Like elements between guide templates 1100 and 1160 areidentified by like reference characters. Guide template 1160 is also amodular template comprising a base 1162 and a mount 1164 removableconnected to base 1162.

As depicted in FIGS. 54 and 55, base 1162 comprises a body 1166 having agenerally circular or ring shaped configuration. More specifically, body1166 has sides 962 and 964 extending between proximal end 958 andopposing distal end 960. Body 1166 also has top surface 954 and opposingbottom surface 956. Body 1166 has an interior surface 1168 that boundsopening 966 extending between surfaces 954 and 956. Top surface 954 ofsides 962 and 964 has a substantially convex curvature extending betweenends 958 and 960. Similarly, bottom surface 958 of sides 962 and 964 hasa substantially concave curvature extending between ends 958 and 960. Itis noted in this embodiment that both first guide rail 982 and secondguide rail 984 (FIG. 32) have been eliminated.

Body 1166 typically has a minimal thickness so as to minimize size andthus simplify insertion within the tissue. In alternative embodiments,however, all or portions of top surface 954 and bottom surface 956 canbe substantially flat by increasing the thickness of body 1166.

Projecting from proximal end 958 is a support 1170. In contrast tosupport 980 of template 1100, support 1170 has a mounting hole 988extending threrethrough. Two other mounting holes 988 are also formed onside 964. As previously discussed, in one embodiment each mounting hole988 has a central longitudinal axis that is oriented at a differentangle than the others so as to support body 1166 is a suspended positionover the bone. Coupling hole 1103 is also formed on side 964 tofacilitate removable coupling between base 1162 and mount 1164.

Mount 1164 comprises a brace 1172 having a generally arched, L-shapeconfiguration. Brace 1172 has a top surface 1174 and an opposing bottomsurface 1176 each extending between a proximal end 1178 and an opposingdistal end 1180. Brace 1172 also has an inside edge 1182 and an opposingoutside edge 1184 both extending between surfaces 1174 and 1176. Anelongated guide rail 1186 projects from bottom surface 1176 along oradjacent to inside edge 1182. Also projecting from bottom surface 1176at distal end 1180 are spaced apart supports 1188 and 1189.

Although not required, in the depicted embodiment support 1188 isprojecting from the distal end of guide rail 1186. Guide rail 1186 andsupports 1188 and 1189 each have an outside face 1192 that is inwardlyspaced from outside edge 1184 of brace 1172. As such a portion of bottomsurface 1176 extending between outside face 1192 and outside edge 1184forms a resting surface 1194. Extending through brace 1172 at distal end1180 at a location between supports 1188 is a mounting hole 1196. Acoupling hole 1114 extends through brace 1172 at proximal end 1170.

Turning to FIG. 56, in the assembled configuration mount 1164 ispositioned on base 1162 so that coupling holes 1103 and 1114 are alignedand supports 1188 and 1189 are positioned at distal end 960 of base1162. More specifically, outside face 1192 of guide rail 1186 andsupports 1188 and 1189 are positioned against interior surface 1168 ofbase 1162 while resting surface 1194 (FIG. 55) of mount 1164 ispositioned on top surface 954 of base 1162. Outside face 1192 andinterior surface 1168 are typically designed having a complementaryconfiguration so that a close tolerance fit is formed between mount 1164and base 1162.

In contrast to guide template 1100 where supports 978 and 979 are atleast partially positioned outside of opening 966 bounded by base 1102(FIG. 48), in guide template 1160, supports 1188 and 1189 are positionedcompletely within opening 966 bounded by base 1162. In further contrast,mounting hole 1196 is formed on mount 1164 rather then base 1162 and ispositioned so as to be in alignment with opening 966 as opposed to beingoutside of opening 966. In alternative embodiments, it is appreciatedthat two or more mounts can be formed for attachment to base 1102, eachmount having a separate support.

In the above assembled configuration, a handle, such as handle 1116 inFIG. 48, is used to removably hold mount 1164 and base 1162 together bypassing through coupling holes 1103 and 1114. The assembled guidetemplate 1160 is positioned on femur 530 in substantially the sameorientation as guide template 950 in FIG. 32. Specifically, opening 966of base 1162 is positioned over trochlear groove 539 so that support1170 is resting on the bone either on the perimeter edge of or justoutside of the articular cartilage. Support 1170 is positioned so as tobe in alignment with trochlear groove 539. Supports 1188 and 1189 restagainst lateral condyle 535 and medial condyle 537, respectively.

In the above mounted position, screws 990 or other fasteners are passedthrough mounting holes 988 and 1196 so as to secure guide template 1160to femur 530. It is appreciated that a guide sleeve 1120 (FIG. 50) canbe used in association with each of mounting holes 988 and 1196. In thisconfiguration, guide template 1160 is supported on femur 530 by supports1170, 1188, and 1189 and by screws 990 or other fasteners. It is notedthat the mounting holes and associated screw or fasteners comprise meansfor securing mount 1164 and base 1162 to femur 530. Other removableanchors and fastening techniques can also be used.

Turning to FIG. 57, in contrast to guide template 1100 where mount 1104is removed prior to rasping, mount 1164 is retained on base 1162 ofguide template 1160 during initial rasping or removal of the bonebounded by opening 966. In one embodiment, rasp 1146, as previouslydiscussed with regard to FIG. 51, can be used to remove the bone boundedwithin opening 966 of guide template 1100. Rasp 1146 is designed toreciprocate along an axis extending between proximal end 958 and distalend 960. Depicted in FIG. 57 is an alternative embodiment of a rasp 1200incorporating features of the present invention. Rasp 1200 is design toreciprocate along an axis extending between opposing sides 964 and 966.Depending on the situation, different orientations for the rasp may bemore convenient for use.

As depicted in FIG. 58, rasp 1200 comprises a handle 1202 having a head1204 mounted on the end thereof. Head 1204 comprises a slide rest 1206and a cutting mount 1207. Slide rest 1206 has a bottom surface 1208 thatis designed to ride on top surface 954 of base 1162. Handle 1202 is setback from bottom surface 1208 so as to form a shoulder 1210 betweenhandle 1202 and head 1204. The formation of shoulder 1210 enables thebottom surface of handle 1202 to ride on top surface 1174 of brace 1172when slide rest 1206 is riding on base 1162. Here it is noted that oncescrew 990 is inserted within mounting hole 1196, handle 1116 cantemporarily be removed from coupling holes 1103 and 1114 so that handle1116 does not interfere with rasp 1200.

Cutting mount 1207 has a cutting surface 1212 having apposing sides 1214and 1216 extending between a proximal end 1218 and an opposing distalend 1220. Cutting surface is comprised of a plurality of teeth, such asteeth 1020 shown in FIG. 37. Because of the orientation of the movementof rasp 1200, a ridge 1222 is formed thereon that extends betweenopposing sides 1214 and 1216. Ridge 1222 has an apex along the lengththereof having a transverse cross section with a convex curve. Inaddition, the sides of ridge 1222 slope into concave curves on theproximal and distal side of ridge 1222.

By reciprocating rasp 1200 side to side within opening 966 and advancingrasp 1200 between proximal end 958 and distal end 960, recessed pocket942 as shown in FIG. 40 is substantially formed. In alternativeembodiments, rasp 1200 need not be reciprocated but could be moved in asmall circular pattern or have other movement to facilitate removal ofthe bone. Likewise, rasp 1200 could be replaced with a mill or otherapparatus to remove the bone. To complete the formation of recessedpocket 942, mount 1164 is removed from base 1162. A rasp, mill or otherstructure is then used to remove the portion of the bone that wascovered by mount 1164. Thus any damage to the articular cartilage thatmay have previously been caused by supports 1188 and 1189 riding on thearticular cartilage during the original rasping or by screw 990 passingthrough mounting hole 1196 of mount 1164 is irrelevant because thatportion of the articular cartilage is removed. Once recessed pocket 942is complete, base 1162 is removed and implant 1064 is secured therein aspreviously discussed.

Set forth above are several different embodiments of the presentinvention. Other embodiments are also disclosed in the '941 application.It is appreciated that the different features of the differentembodiments can be mixed and matched to produce a variety of otherembodiments within the scope of the present invention. By way of exampleand not by limitation, each of the different implants can be made withor without an inlay of porous bone ingrowth material on the boneapposition surface; each different implant can have one or moredifferent lines that are connected in one or more different ways; andeach different implant can be made as an integral body or two or moreseparate parts. For example, each implant can comprise a metal tray thatis mounted to the bone and a plastic bearing plate that is mounted tothe tray. It is likewise appreciated that the different methods stepsfor the different embodiments can also be mixed and matched and usedwith other techniques. For example, the guide template having supports,such as supports 978-980, that are either fixed or removable can be usedfor resecting any type of articulation surface on any joint. Finally, itis again noted that the implants described herein are only by way ofexample and not by limitation. The present invention can also be used inassociation with resurfacing articulation surfaces of other orthopedicjoints.

Finally, the above embodiments primarily discuss mounting implants onresected articulation surfaces. On occasion, however, a sufficientportion of a natural articulation surface has been worn down orotherwise removed by events other than surgical resection so that it isnot necessary to resect the wear surface which is still functioning as anatural articulation surface. On these occasions, it is envisioned thatthe implant can be mounted directly on the worn natural articulationsurface with minimal or no surgical resection of the articulationsurface.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A guide template for use in resurfacing a portion of a bone, theguide template comprising: a body adapted for positioning over a naturalor resected articulation surface of a bone and having a top surface andan opposing bottom surface that each extend between a proximal end andan opposing distal end, the body at least partially bounding an openingextending between the top surface and bottom surface, at least a portionof the top surface or the bottom surface having a convex curvature orconcave curvature that extends between the proximal end and the opposingdistal end; at least three spaced apart supports projecting below thebottom surface of the body such that the body can be supported by thesupports; and means for securing the body to the bone.
 2. The guidetemplate as recited in claim 1, wherein at least one of the supports isremovably connected to the body.
 3. The guide template as recited inclaim 1, wherein at least two of the supports are removably connected tothe body.
 4. The guide template as recited in claim 1, furthercomprising: a base comprising the body and having a least one of thesupports projecting therefrom; and a mount comprising a brace having atleast one of the supports projecting therefrom, the mount beingremovably coupled to the base.
 5. The guide template as recited in claim1, wherein the base has the opening extending therethrough and whereinwhen the mount is coupled with the base, the at least one support isdisposed within the opening.
 6. The guide template as recited in claim1, wherein at least two spaced apart supports are located at the distalend of the body and at least one support is located at the proximal endof the body.
 7. The guide template as recited in claim 1, wherein atleast a portion of the top surface of the body has a convex curvatureand wherein at least a portion of the bottom surface of the body has aconcave curvature.
 8. The guide template as recited in claim 1, whereinthe opening is bounded by an interior surface, the interior surfacecomprising: a substantially linear first side section; a substantiallylinear second side section opposing the first side section; a proximalsection; and a distal section, the distal section having an asymmetricalcurvature.
 9. The guide template as recited in claim 1, wherein theopening has an area of at least 2 cm².
 10. The guide template as recitedin claim 1, wherein the body completely encircles the opening.
 11. Theguide template as recited in claim 10, wherein the opening isasymmetrical.
 12. The guide template as recited in claim 1, wherein themeans for securing the body comprises a first hole extending through thebody and a first fastener adapted to extend through the first hole. 13.The guide template as recited in claim 12, further comprising a tubularguide sleeve slidably disposed within the first hole, the first fasteneradapted to extend through the guide sleeve.
 14. The guide template asrecited in claim 1, wherein the means for securing the body comprises aplurality of holes formed on the body, each hole having a centrallongitudinal axis extending therethrough, the central longitudinal axisof each hole being oriented at an angle different than the others. 15.The guide template as recited in claim 14, further comprising a tubularguide sleeve slidably disposed within a first hole selected from theplurality of holes, the first hole having a length and the tubular guidesleeve having a length greater than the length of the first hole. 16.The guide template as recited in claim 14, further comprising aplurality of screws, each of the plurality of screws being adapted to bereceived within a corresponding one of the plurality of holes.
 17. Theguide template as recited in claim 1, further comprising an elongatedfirst guide rail upwardly projecting from the surface of the body. 18.The guide template as recited in claim 17, further comprising anelongated second guide rail upwardly projecting from the top surface ofthe body on a side of the opening opposite the first guide rail.
 19. Aguide template for use in resurfacing a portion of a bone, the guidetemplate comprising: a base adapted for positioning over a natural orresected articulation surface of a bone and having a top surface and anopposing bottom surface that each extend between a proximal end and anopposing distal end, the base at least partially bounding an openingextending between the top surface and bottom surface; means for securingthe base to the bone; and a mount having a first support projectingtherefrom, the mount being removably connected to the base so that thefirst support projects below the bottom surface of the base, the firstsupport resting against the bone when the base is secured to the bone.20. The guide template as recited in claim 19, further comprising asecond support projecting from the mount so that the second supportprojects below the bottom surface of the base.
 21. The guide template asrecited in claim 19, further comprising a support connected to the baseand projecting below the bottom surface thereof.
 22. The guide templateas recited in claim 19, wherein at least a portion of the top surface ofthe base has a convex curvature and wherein at least a portion of thebottom surface of the base has a concave curvature.
 23. The guidetemplate as recited in claim 19, wherein the opening is asymmetrical.24. The guide template as recited in claim 19, wherein the means forsecuring the base comprises a first hole extending through the body anda first fastener adapted to extend through the first hole.
 25. The guidetemplate as recited in claim 24, further comprising a tubular guidesleeve slidably disposed within the first hole, the first fasteneradapted to extend through the guide sleeve.
 26. The guide template asrecited in claim 19, further comprising means for securing the base tothe bone.
 27. A method for mounting a trochlear implant, the methodcomprising: forming a recessed pocket at the distal end of a femur wherethe distal end of the femur is not otherwise resected, the pocket beingformed by resecting at least a portion of the femur forming thetrochlear groove, the recessed pocket having a floor with side wallupstanding around a perimeter thereof, an elongated channel is formed onthe floor at a location at least substantially in alignment with thelocation of the trochlear groove; and securing an implant within thepocket.
 28. The method as recited in claim 27, wherein the step offorming the recessed pocket comprises: positioning a guide template atthe distal end of a femur, the guide template at least partiallybounding an opening that is disposed over at least a portion of thetrochlear groove of the femur; and moving a rasp within the opening ofthe guide template so that the rasp removes at least a portion of thefemur aligned with the opening of the guide template.
 29. The method asrecited in claim 28, wherein the step of positioning comprises: placingthe guide template at the distal end of the femur; and advancing a screwthrough a tubular guide sleeve and into the femur, the tubular guidesleeve being slidably disposed within a mounting hole formed on theguide template.
 30. The method as recited in claim 27, furthercomprising creating a tunnel through the distal end of the femur, thetunnel having a first end formed in the pocket and an opposing secondend disposed outside the pocket.
 31. The method as recited in claim 30,further comprising securing an anchor within the tunnel, a flexible lineor shaft extending between the implant and the anchor so as to securethe implant within the pocket.